Metal parts can be prepared using powdered metallurgy (P/M) from powdered metal compositions by methods known within the industry. These parts can be formed in shapes which would be difficult to form by other methods. Many applications for parts formed from P/M processes require high strength and dynamic properties. It is necessary to re-engineer or increase the density of the composition to meet the requirements. However, the methods available for obtaining high density, high strength parts by P/M processes such as high temperature sintering, double-press and double-sintering processes, and liquid phase sintering have been found to have inherent limitations.
Recently, U.S. Pat. No. 5,154,881 disclosed a composition which provided a single compaction method for obtaining high density parts. This patent utilizes an iron-based metal powder composition containing an amide lubricant. The lubricant is a reaction product of a monocarboxylic acid, a dicarboxylic acid, and a diamine. The composition, metal and lubricant, is compacted in the die of the temperature of up to about 690.degree. F., and preferably in a range of 300-500.degree. F., at a pressure of about 35-60 tons per square inch (tsi). Further disclosed is the fact that the composition can be warm-pressed at a temperature of about 300.degree. F. However, the properties achieved using the materials and method described in this patent are not sufficient to meet the needs of all applications.
Therefore, a need exists to develop a process for preparing parts which have improved impact strength and tensile properties. Parts which have these properties would be expected to have longer life and be less subject to wear.